craigtp

Advanced Distributed System Design Course - Udi Dahan

Notes by Craig Phillips

Fallacies of Distributed Computing

• There are 11 fallacies of Distributed Computing:
  1. The network is reliable
  2. Latency isn’t a problem
  3. Bandwidth isn’t a problem
  4. The network is secure

5. The topology won’t change

craigtp

OK so now you have implemented the kata. Your tests should look something like this:

We can say that the tests define the object "in a calculus of itself".
They are not state based tests, they define how the behaviours of the object interact with each other.

To see the real value of this let's introduce some change ... I hear real system's do this occasionally.
Because this is a high performance system decimal math is too slow. You now need to use floats instead. 

Need help on floating point math? Check out: http://www-users.math.umd.edu/~jkolesar/mait613/floating_point_math.pdf

craigtp

Value objects are an important concept in DDD. This kata is made both to learn value objects and to learn better ways of testing.

Write a probability value object. It should contain the following methods:
   Probability CombinedWith(Probability)
   Probability InverseOf()
   Probability Either(Probability)

if you forget your probability math:
   Either:P(A) + P(B) - P(A)P(B)
   CombinedWith: P(A)P(B)

craigtp

Keybase proof

I hereby claim:

• I am craigtp on github.
• I am craigtp (https://keybase.io/craigtp) on keybase.
• I have a public key whose fingerprint is 8FBD 50F4 7D2C E90F 95D6 1B27 3965 4610 07EB B49F

To claim this, I am signing this object:

craigtp

gci -recu -inc "*.*" | % { $_.LastWriteTime = Get-Date }

craigtp

public static class NumericHelpers
    {
        // Float point maths is whack.  We can't check for absolute equality as floating point numbers are imprecise
        // and are subject to rounding issues (See: http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html)
        // Therefore, we can't check for absolute equality, but instead we have to need to check for values being
        // "nearly" equal, which allows a small margin of error (i.e. something known as the "Epsilon" value for
        // the given data type for this CPU that this code is running on).
        public static bool NearlyEqual(double a, double b, double epsilon)
        {
            var absA = Math.Abs(a);

craigtp

Option Explicit 

Dim objshell,path,DigitalID, Result 
Set objshell = CreateObject("WScript.Shell")
'Set registry key path
Path = "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\"
'Registry key value
DigitalID = objshell.RegRead(Path & "DigitalProductId")
Dim ProductName,ProductID,ProductKey,ProductData
'Get ProductName, ProductID, ProductKey

craigtp

using System;
using System.Text;

namespace RandomString
{
    public class RandomString : IDisposable
    {
		// Can use the BetterRandom class here or just use the built-in System.Random class.
        private BetterRandom random = new BetterRandom();
        private const string alpha_selection = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

craigtp

public static class StringExtentionMethods
{
	public static string TruncateAtWord(this string input, int maxlength, bool addEllipsis)
	{
		if (input == null || input.Length <= maxlength) return input;
		var ellipsisLengthDeduction = (addEllipsis ? 3 : 0);
		var iLastSpace = input.LastIndexOf(" ", (maxlength - ellipsisLengthDeduction), StringComparison.Ordinal);
		var iLength = 0;
		if (iLastSpace < 0)
		{

craigtp

# Run this as Administrator
net stop w3svc
Get-ChildItem "C:\Windows\Microsoft.NET\Framework*\v*\Temporary ASP.NET Files" -Recurse | Remove-Item -Recurse -Force
net start w3svc